1. Field of the Invention
This invention relates to an annular transition duct connecting the last stage of a compressor turbine to a single stage of a power turbine of a two-shafted gas turbine.
2. Description of the Prior Art
This invention is an improved form of the invention described in copending application Ser. No. 620,608, filed Oct. 8, 1975 of common assignee. In the above-identified application the annular transition duct for a two-shafted gas turbine is shown having diverging opposed walls or shroud members neccessitated by the variation in annular diameters between the last stage of the compressor turbine and the single stage power turbine. In order to maintain the velocity of the working fluid generally undiminished as it passes therethrough, the duct contains stationary vanes having a particular configuration and angular relationship to offset the otherwise increasing area provided by the diverging shrouds. Variable vanes are also disposed within the shrouds generally downstream of the stationary vanes to direct the working fluid into the power turbine stage at an angle determined by the intended speed of operation of the power turbine. Also, a constant clearance was maintained between the ends of the variable vanes and the adjacent shroud member by each end of the vane and the adjacent shroud member defining a spherical segment having common centers to define concentric arcuate surfaces. The axis of the angular movement of the variable vane was angled with respect to the axis of the turbine so that the discharge end of the transition zone was substantially tangent to the entry into the power turbine stage providing a flow path free of abrupt directional changes. In the instant application, all the above features remain, however, the variable vanes of the instant application are disposed immediately adjacent the downstream edge of the stationary vanes to form a single generally continuous airfoil surface across the axial extent of the transition zone. Further, particular mounting structure is shown which permits transient growth in the shroud or vanes while maintaining their set angular position and clearance between adjacent parts.